Eelgrass beds in central Salish Sea are critical components of healthy ecosystems that are vulnerable to anthropogenic impacts. This study utilized two locations in Possession Sound to monitor water chemistry within and near two different eelgrass beds; one unmapped, and one established. The study compared these two locations and investigated the impact of location on water chemistry within the bed. Data-sharing and collaboration with the Samish Indian Nation Department of Natural Resources’ work on eelgrass beds in Fidalgo Bay provided a broader scope into regional differences within the central Salish Sea. This study was conducted by Ocean Research College Academy (ORCA) students at eelgrass beds in Possession Sound located near Mukilteo and Hat Island. The study ran from October 2019 to spring 2020, and utilized background data from past studies to inform studies at the bed near Mukilteo. Data were collected using a combination cast of a camera collecting visual data and a CastAway CTD, which collected vertical profiles of salinity and temperature at recorded geographic coordinates. Data were collected during a free drift across the eelgrass bed. An EXO Sonde was temporarily installed in the bed to collect chlorophyll and turbidity data in a longitudinal manner. The study primarily explored how location impacts the water chemistry eelgrass beds in central Salish Sea both within the bed and within a region. Research going forward could study remote beds more comprehensively using technology previously tested such as drones and SONAR, as well as a longer-term collaboration between the Samish DNR and ORCA.

Nitrate, silicate, and phosphate are essential nutrients in diatom based food webs. Chlorophyll and nutrients are good indicators of phytoplankton abundance and diversity. Phytoplankton, being integral to the Possession Sound ecosystem, can be indicators of greater change in an ecosystem. By studying phytoplankton abundance and diversity along with chlorophyll and nutrient levels spatially and temporally, correlation can be determined and used to help understand the health of Possession Sound. It was predicted that nutrients and chlorophyll abundance are inversely proportional, while chlorophyll and phytoplankton abundance and diversity are directly related. Thus, higher nutrient levels indicate less chlorophyll and fewer nutrients indicate higher chlorophyll and plankton abundance and diversity. Increased levels of nutrients in the fall and winter were expected, with greater chlorophyll and plankton levels in the spring and summer. The chlorophyll and plankton abundance and diversity were anticipated to have gone down over the past four years, while nutrient levels will have gone up slightly. Students at the Ocean Research College Academy (ORCA) collect monthly samples as part of the longitudinal study: State of Possession Sound (SOPS). Results from three locations were utilized from 2016 to 2019. Chlorophyll is measured by a YSI EXO2 Sonde, while nutrient samples are taken using the Niskin bottle and sent to the University of Washington Marine Chemistry lab to test for results. By evaluating seasonal data, temporal trends of chlorophyll, nutrients, and plankton abundance and diversity were discovered. Changes in data can be linked to environmental and anthropogenic variations. It would be compelling to analyze ecosystem changes by exploring dissolved oxygen and pH levels.